Metal shafts having a circular section have been widely used as typical rotating shafts (drive shafts and driven shafts) for an image forming apparatus and a sheet conveyance device such as a rotating shaft of, for example, a conveyance roller. Nowadays, however, from the viewpoints of productivity and cost, rotating shafts formed by bending sheet metal into a U shape are also used. FIG. 11A illustrates a rotating shaft 90 formed by bending sheet metal into a U shape.